ChemCatChem最新文献

Performing designed, abiotic chemical transformations in live environments represents a powerful approach to interrogate and manipulate biology, and to uncover new types of biomedical tools. Despite significant advances in the area, the list of bio-orthogonal reactions so far available is still very short, and mainly restricted to the use of strained reactants, or metal-promoted processes. En route to further expanding the repertoire of biocompatible reactions, we demonstrate here that aryldiazonium salts, well-established as radical precursors, can react with unsaturated systems in biologically relevant media under photocatalytic conditions, to give either addition or cycloaddition products, depending on the reactants.

The Front Cover illustrates the generation of carbon radicals through the cleavage of carbon–sulfur bonds in alkyl benzothiazolyl sulfides by using Hantzsch ester. In their Research Article (DOI: 10.1002/cctc.202401427), T. Sengoku and co-workers report how they successfully achieved this radical generation under blue light by two methods: one employing caesium carbonate and the other combining 4DPAIPN with potassium carbonate. This approach provides a more direct synthetic route by avoiding the preparation of sulfone intermediates and demonstrates its utility in the synthesis of C-glycoside.

The transformation of biomass-derived furan-based platform compounds into etherification products over Pd-based catalysts is an effective pathway for the production of fuel additives. Specifically, furfuryl ethyl ether (FEE) can be synthesized through the reductive etherification of furfural (FAL). However, the utilization of Pd-based catalysts in the reductive etherification is limited by high Pd loadings. Herein, ECNU-28 nanosheet, derived from a zeolitic precursor with the layered structure analogous to SZR framework, was utilized as a support for Pd loading (low as 0.2 wt.%), producing a bifunctional catalyst Pd/ECNU-28 for the furfural reductive etherification reaction. The large external surface area (148 m² g⁻¹) of ECNU-28 facilitates the access of the reaction substrates to the acid sites. Meanwhile, the moderate acid site strength of ECNU-28 reduces the ring-opening side reaction of the etherification product, and its special inclined 8-ring restricts the reductive etherification reaction to occur on the surface. The Pd/ECNU-28 catalyst exhibited a superior etherification product yield, up to 83.1%. In addition, providing much higher FEE productivity per gram of Pd (6648 mmol_FEE g_Pd⁻¹ h⁻¹) than previously reported catalysts. Benefiting from the inherent hydrothermal stability of aluminosilicate, the Pd/ECNU-28 catalyst possesses good recyclability and can undergo regeneration treatment through simple calcination.

Y. Qiao, R. Xin, J. Ge, ChemCatChem 2024, 16, e202401116

The funding information for this work was missed:

Acknowledgements

Authors would like to thank the Beijing Natural Science Foundation (L212019), the National Key R&D Program of China (2023YFA0913600), Tsinghua University Initiative Research Program (2023Z02ORD001) and Key Technologies R&D Program of Guangdong Province (2022B1111050002) for their financial support.

We apologize for this error.

Residential stoves, commonly used for heating, are a significant source of emissions due to the harmful substances produced during biomass combustion, yet they remain largely unregulated. The use of catalytic systems presents a promising approach for mitigating these emissions. This study investigates the potential of Cu–Mg–Mn–Al and Co–Mg–Mn–Al mixed metal oxides, synthesized from hydrotalcite precursors via coprecipitation and calcination, for reducing emissions of CO, C₃H₈, and CH₄. The physicochemical properties of the catalysts were thoroughly characterized using techniques such as AAS, XPS, XRD, H₂-TPR, CO₂-TPD, and NH₃-TPD. Catalytic performance was evaluated over a temperature range of 100–500 °C in both two-component (CO + C₃H₈ or CO + CH₄) and three-component (CO + C₃H₈ + CH₄) gas mixtures with oxygen. Results revealed that Co-based catalysts outperformed Cu-based ones in catalytic activity. However, in the three-component mixture, catalytic activity decreased, likely due to competitive adsorption and interactions with active oxygen species. These preliminary findings underscore the potential of mixed metal oxides for emission control in residential stoves, setting the stage for further optimization and application.

Various chemical transformation approaches are being actively developed to address the environmental accumulation of plastic waste. However, most postconsumer plastics are heterogeneous, exhibit high melt viscosity, and are insoluble in most conventional solvents. Such properties result in transport-limiting chemical transformations, low conversion rates, and low product selectivity. Although supercritical fluids (SCFs) have been a matter of continuing scientific interest in several mass-transfer processes, the use of SCFs as tunable media for the chemical transformation of postconsumer plastics is still in its early stages, but has rapidly advanced in recent years. Therefore, this review reports on the current state-of-art of chemical transformation of plastics using SCFs. It addresses the effects of sub and supercritical CO₂ (scCO₂) on solvolysis-based technologies. Additionally, it reviews recent advances on the use of supercritical organic solvents (e.g., ethanol, methanol) and supercritical water (SCW) as reaction media for the solvolysis and liquefaction of plastics, respectively, and the latest developments in the simultaneous conversion of CO₂ and waste plastics. Overall, developing technologies that minimize mass transfer limitations during the chemical transformation of plastics is critical to overcoming some of the major bottlenecks hampering product yield and selectively, and ultimately the economic viability of plastics recycling and upcycling.

Dilute atom alloys (DAAs) are an important class of heterogeneous catalysts due to their ability to precisely tune the activity and selectivity of reactions. DAA catalysts typically consist of a small quantity of metal solute in a metal host. Key considerations in the stability of DAA catalysts are the segregation and aggregation energy. In this work, we report a systematic theoretical study of segregation and aggregation energies of DAA catalysts composed of 3d, 4d, and 5d transition metals. To investigate the nature of DAAs, we analyzed both Bader charge and density of states, as well as formation energies, to identify the most stable DAA configuration for a given alloy. We further applied regression-based, tree-based, and neural network machine learning (ML) models to gain physics-based insights in predicting segregation and aggregation energies based on readily available atomic and bulk features. We found that the d-band filling of the solute and host, nearest neighbor distance of the host, and d-band width of the solute determine the segregation energy, whereas the Pauling electronegativity of the host and solute, nearest neighbor distance of the host, and cohesive energy of host determine aggregation energy. Our findings provide crucial insights for DAA catalyst design.

ChemCatChem 2022, 14, e202200013

DOI: doi.org/10.1002/cctc.202200013

H.-L. Du, M. Chatti, B. Kerr, C. K. Nguyen, T. Tran-Phu, D. A. Hoogeveen, P. V. Cherepanov, A. S. R. Chesman, B. Johannessen, A. Tricoli, R. K. Hocking, D. R. MacFarlane, A. N. Simonov, Durable Electrooxidation of Acidic Water Catalysed by a Cobalt-Bismuth-based Oxide Composite: An Unexpected Role of the F-doped SnO₂ Substrate, ChemCatChem 2022, 14, e202200013.

It has come to our attention that the affiliation for Bernt Johannessen was incomplete in this article. The correct and full affiliation should read “Australian Synchrotron, ANSTO, Clayton VIC 3168, Australia”. We apologize for this oversight. This correction does not affect the scientific conclusions of the article in any way.

Heterogeneous rhenium catalysts supported on various oxides, particularly TiO₂, have demonstrated effectiveness in converting carbon dioxide (CO₂) to methanol via hydrogenation, showing high selectivity under diverse reaction conditions. However, the impact of different rhenium precursors on the catalytic performance and physicochemical properties of ReO_x/TiO₂ has not yet been elucidated. Herein, we compared catalysts prepared from NH₄ReO₄ and Re₂O₇ precursors with varying rhenium content (4–14 wt% Re) synthesized using a wet impregnation approach. These catalysts were evaluated under different reaction temperatures (200–250 °C), pressures (100–200 bar), and H₂/CO₂ ratios (1–4). This study revealed that both catalytic performance and physicochemical properties varied not only with the type of precursor but also with the rhenium content. Variation in reduction temperature, particle size, oxidation states of Re and surface Re═O terminals were observed. In batch system, catalysts derived from NH₄ReO₄ demonstrated a higher selectivity for methanol production under high pressure and stoichiometric conditions, regardless of temperature. In contrast, Re₂O₇-based catalysts demonstrated higher methanol selectivity at 200 °C, with H₂/CO₂ ratios between 1 and 3, regardless of the total pressure. These findings provide a deeper and valuable insight on the choice of precursors for the preparation of ReO_x/TiO₂ catalysts for CO₂ hydrogenation.

The dry reforming of methane reaction is a promising means to convert two potent greenhouse gases, methane and carbon dioxide, into industrially valuable synthesis gas. However, the presence of reducing gases and high operating temperatures degrade conventional nickel catalysts via excessive coke formation and particle sintering. These catalysts are not readily regenerated because the oxidative heat treatments employed to remove coke further promote active particle sintering. Herein, we designed high entropy aluminate spinel oxides (MAl₂O₄ where M = Co, Mg, Ni, and divalent site vacancies in nominal equimolar concentration) as selective and regenerable reforming catalysts. Under reaction conditions, reducible nickel and cobalt cations exsolved from the spinel lattice to form highly selective bimetallic particles on the oxide surface. Instead of sintering, these particles uniquely redissolved back into the aluminate lattice upon reoxidation and regained the original spinel structure. This phenomenon is ascribed to entropic stabilization, wherein an increase in configurational entropy creates a thermodynamic driving force for redispersing supported metal particles back into the multi-cationic oxide structure. During the dry reforming reaction, nickel atoms similarly exsolved from a NiAl₂O₄ sample and reduced to form metallic nickel particles. However, subsequent oxidation of this sample promoted sintering and oxidation of the nickel particles to an inactive state. High entropy materials thus provide a unique mechanism of regeneration, which is inaccessible in conventional catalysts.